The Developer Toolbar, accessible via the shift-F2 keyboard shortcut or from the Web Developer menu, is intended to provide easy access to Web development tools, particularly those that don't have another form of user interface.
Its most significant feature is a command line interface (CLI), typically dreaded or ignored by casual users but often beloved by programmers. The Firefox CLI promises to accelerate development work, based on the premise that typing produces results faster than mousing across screens and through menus.
"This command line is designed to be quick-to-type and discoverable," said Mozilla product manager Kevin Dangoor in a blog post. "It will complete commands and parameters for you, to save you typing."
The CLI allows developers to: access the Web Console (a UI for viewing information about Web page log messages); control the Debugger; open the Style Editor (for altering CSS files); open the Page Inspector (a UI for viewing Web page elements); control the Responsive Design View (for viewing mobile versions of Web pages or apps); and control Tilt, a 3-D Web page visualization tool.
As an example, typing "resize to 320 480" into the CLI will resize the displayed Web page to fit a 320x480 pixel mobile phone screen.
The CLI also allows developers to view and edit cookie files, to take screenshots (instant or timed) of Web pages or of specific elements on a given page, and to alter specific Web page code using the pagemod command.
For example, the command pagemod remove element iframe would strip a page of iframe elements, the mechanism by which ads and widgets are often injected into Web pages from third-party servers.
According to Dangoor, Mozilla will be adding more commands to its CLI in the future and is also planning to demonstrate how users can create and add their own commands.
Beyond the Developer Toolbar, Firefox 16 beta also removes the need to add special code prefixes to utilize recently added Web APIs, including the Battery API, the Vibration API, CSS3 Animations, Transitions, Transforms, Image Values, Values & Units, and IndexedDB.
Editor's note: This story was changed Sept. 4 to correct misstatements about Firefox beta builds and Firefox Aurora builds being identical.